End users often have media collections that are spread across multiple endpoint computing devices (e.g., phones, personal computers, laptops, gaming consoles, tablet devices, etc.) spanning multiple networks. With the advent of fast network connections to most devices, and the ability to maintain almost continuous connectivity for many endpoints, users need not have a local copy of a piece of content in order to access it. However, presently there is no way to know the location of all content in a user's collection from any of the user's endpoint computing devices in the user's domain. Moreover, presently there is no way to make intelligent decisions about selecting a instance of a content item for playback when multiple instances of the same content item are located on different endpoint computing devices so as to maintain a high quality user experience.